This invention relates to telephone systems and more particularly to a key telephone system.
During the course of the following description and when reading the claims, it should be remembered that due to the design and operation of a key telephone system there is a ground employed therein which is actually a positive voltage and is referred to herein as key system positive ground or merely positive ground.
In presently known key telephone systems, which incorporate a rather large number of central office lines, the operator, after placing the operator subset on hold and dispersing the calls to a called party, would have no means of knowing whether calls were answered and placed back on hold by the called party.